Are there showers near walk-in camping sites?

Looks like I missed out on camping pass so will have to do the " walk-in " camping which is purchased the day of ? My question is how far exactly will I have to walk ? Also, does this camping fill up fast ? I expect to arrive Friday afternoon and hope to get a spot. Last question: Is there showers? Thanks to anyone who can advise me since I'm a First Timer So excited!!